This invention relates to an ignition angle advancer for an internal combustion engine and more particularly to an improved arrangement for advancing the spark advance angle of an internal combustion engine in response to changes in throttle position.
In many internal combustion engines, there is provided a mechanical interconnection between the throttle control mechanism and the spark control mechanism for advancing the spark angle in response to opening of the throttle. For example, in outboard motors, it is the common practice to mount a throttle control linkage on the side of the engine which is controlled by a remote cable and which positions the throttle valve of the engine. In addition, a spark advance control lever is mounted coaxially with the throttle control lever and is connected to it by means that include a lost motion connection so that the spark advance will be controlled in response to throttle position. Although such arrangements offer certain advantages, such as compactness, they have a number of disadvantages. For example, the actual magnitude of movement of the spark advance mechanism required to provide the necessary degree of advance is often substantially greater than the relates corresponding angular movement of the throttle valve. In order to achieve such magnified movements, it has been necessary to provide a substantially longer lever arm for the spark advance mechanism than for the throttle mechanism. Due to the placement of the other components of the engine, such long levers are not always possible.
It is, therefore, a principal object of this invention to provide an improved throttle and spark advance mechanism for an internal combustion engine.
It is another object of the invention to provide an improved spark advance mechanism that is controlled by a throttle valve lever and which has an amplified range of movement.
In addition to the aforenoted defect, the prior art constructions have resulted in an arrangement wherein the movement of the spark advance mechanism is directly related to the movement of the throttle valve. However, the actual spark advance desired characteristics of the engine may not have such a linear relationship.
It is, therefore, a further object of this invention to provide an improved actuating arrangement for the spark advance mechanism of an internal combustion engine.
It is a further object of the invention to provide a spark advance mechanism for an internal combustion engine wherein the spark may be advanced in a non-linear relationship relative to the throttle valve movement.